Caution Patients on Diuretics to Protect Themselves on Hot Days

Philadelphia—Pharmacists have an opportunity to help patients taking diuretics stay healthy as the weather warms up.

A report in BMJ One points out that those patients are often at risk for low potassium levels, which increases their risk of cardiac arrhythmias or other issues, especially if they perspire a lot.

Researchers from the Perelman School of Medicine at the University of Pennsylvania determined, however, that taking prescription potassium supplements can reduce those risks by nearly 10%.

At issue in the study was the drug furosemide, marketed as Lasix and prescribed to patients with heart failure, high blood pressure, and/or kidney and liver disease to decrease fluid retention and combat swelling in the arms, legs, and/or abdomen.

As with other diuretics, furosemide causes patients to urinate more than normal, leading to lower levels of potassium in the body. When outdoor temperatures are high and patients sweat, they can lose too much potassium.

“We already know that hot outdoor temperatures are associated with increased risk of heat stroke, dehydration, heart disease, respiratory diseases, and higher risk of death overall, but people who take furosemide and have insufficient intake of potassium are at increased risk,” explained senior author Sean Hennessy, PharmD, PhD, a professor of Epidemiology and Systems Pharmacology and Translational Therapeutics. “As outside temperatures increase, the apparent survival benefit of potassium also increases.”

The study looked at 1999–2010 data from U.S. Medicaid patients in California, Florida, New York, Ohio, and Pennsylvania, which make up about 40% of total U.S. Medicaid enrollees. The focus was on more than 300,000 patients who took 40 mg/day or more of furosemide, 32% of them also using potassium supplements when they initiated the diuretic.

Using daily temperature data from the National Oceanic and Atmospheric Administration, researchers determined that, across all temperatures, the potassium-taking group experienced a 9.3% lower risk of death than the group who did not take potassium. This survival benefit also rose with daily maximum temperatures.

“These findings suggest that potassium intake may be important for patients taking furosemide, especially on hot days,” added lead author Young Hee Nam, PhD, a postdoctoral researcher in Biostatistics, Epidemiology and Informatics. “It is also important to understand that our findings do not imply that more potassium is better, and do not imply that prescription potassium may be beneficial for all patients. Further studies are needed to find out the generalizability of our findings to other patient populations. The best way to reduce harmful effects of high temperatures on mortality might be to avoid exposure to high temperatures if possible.”